Table of Contents
Cement and Concrete Research
The journal Cement and Concrete Research welcomes manuscripts on fundamental questions of materials science. Articles can deal with concrete technology, fiber reinforcement, waste management, recycling, life cycle analysis, and novel concretes. This journal also welcomes rapid communications. The journal seeks papers that have a broad scope, are of high quality, and are novel. Moreover, papers should address new concepts and technologies in concrete and cement.
Impacts of cement and concrete on the environment
The use of cement and concrete generates a significant amount of CO2 emissions and is a contributing factor to global warming. CO2 is the primary greenhouse gas and traps heat in the earth’s atmosphere. Cement production also contributes to the emission of SO2 and NOx. China’s cement industry releases about 4% of SO2 and 10% of NOx annually. Researchers from the University of California, Davis, used an environmental impact assessment methodology to analyze the impacts of concrete production. This methodology takes into account the variability and uncertainty inherent in data and allows for an analysis of the probability of reducing GHG emissions, air pollutants, and other environmental impacts.
The production of cement and concrete consumes approximately 10% of the world’s industrial water, which strains existing water supplies. Furthermore, concrete also contributes to surface runoff, which is an important component of urban flooding. In addition, concrete contributes to heat-island effects in cities, as it absorbs the sun’s heat. It also traps the gases from air conditioning units and car exhausts.
The carbon dioxide (CO2) emissions produced by cement production are proportional to the amount of cement in a concrete mix. A single ton of cement releases about 900 kilograms of CO2. This accounts for up to 88 percent of the total emissions of an average concrete mix. Cement manufacture also contributes to the generation of greenhouse gases indirectly, via fossil fuel combustion and energy use.
Materials used in cement and concrete
In cement and concrete research, a range of different chemicals are added to improve the properties of the cement. These chemicals include accelerators, plasticizers, dispersants, and water-reducing agents. They increase the workability of the cement and the strength of the concrete after application. They also reduce the amount of water required for the concrete to set up, which results in lower material requirements and reduced energy consumption. In addition, they reduce the amount of cement needed for a strong, durable concrete.
During the 1930s, the United States led the world in cement research and technology. However, since then, Europe and Japan have been moving ahead. To address this, the National Science Foundation established the Center for Science and Technology of Advanced Cement-Based Materials at Northwestern University. Its goal is to develop the science required to create new cement-based materials that can be used for new construction, power plant restoration, and waste-disposal systems.
Materials used in cement and concrete research can range from traditional cements to novel synthetic materials. Fly ash, a byproduct from coal-burning power plants, is one example of a new compound being studied. This material contains small amounts of lime and aluminosilicate and is currently being investigated as a pozzolanic material for concrete.
Supersulfated cements are composed of 80% ground granulated blast furnace slag, 15% gypsum, and a small amount of lime as an activator. They produce strong concretes and are resistant to aggressive agents. Calcium aluminate cements, on the other hand, are made from limestone and bauxite. Calcium aluminate cements are particularly useful for high-temperature concretes.
Methods of accelerated curing
Accelerated curing methods are a way to increase the strength of concrete by exposing it to higher temperatures. The exact methods vary according to the type of concrete and its size and shape. In general, accelerated curing is more effective for high-strength concrete than for lower-strength concrete.
The first method involves raising the temperature of curing water. This method is suited for early curing of concrete and is often used in pre-cast construction. It is also applied in repair works in which concrete needs to be functional early. By raising the temperature of the curing water, accelerated curing of concrete can be achieved in a shorter period of time.
Accelerated curing requires fewer days for the concrete to attain its desired ultimate strength. The concrete’s compressive strength is typically measured at three, seven, or 28 days after it is poured. The ultimate strength of the concrete is generally more than 6,000 pounds per square inch.
Another way to accelerate concrete curing is by using an external heat source. The heat will cause water to hydrate into the cement more quickly. As a result, the compressive strength of concrete is achieved in a shorter time.